Generally speaking, a structure that is adopted in a bicycle to achieve an effect of braking by hydraulic transmission can be classified as a control-by-wire hydraulic brake, where a brake grip is provided with a brake wire that is connected to a transmission component, and a fully hydraulic brake structure, where a transmission components are directly installed in the brake grip and the transmission components comprise at least a fluid reservoir, a piston, and connection rod (or a transmission arm), in which the transmission components are operatively coupled to the brake unit and the brake unit comprises at least one caliper (or clamping arm) and two brake shoes.
The present invention is made to provide a control-by-wire hydraulic bicycle brake structure that comprises a brake wire provided at a brake grip for connecting a transmission component to actuate a brake unit. A known prior art related to such a structure will be discussed in the following.
Taiwan Utility Model Publication No. 476324 discloses a master cylinder structure for bicycle disc brake, which features easy installation and excellent resistance against penetration and leakage. Internal threading is formed on an external circumference of a front section of a mounting seat and internal threading is formed inside a corresponding tubular section. The mounting seat forms a space for receiving a spring. A guide slot is formed in the space at a location close to a front end to receive an O-ring to fill therein. A brake wire coupler has a front section from which an elongate bar section extends into the tubular section to abut a hydraulic cylinder body and has an end forming a head. The head forms a fixing hole longitudinally extending therethrough to receive a fixing bolt to engage therein to fix a brake wire. The head forms a recess inside the fixing hole to receive an opening rim of a dust cap to fit therein.
However, the brake wire is directly coupled to a piston. When a user wishes to make an adjustment of the brake wire, such as stretching the brake wire, the piston is also caused to move, making hydraulic fluid access hole blocked thereby converting the interior of the hydraulic cylinder into a closed system, thereby leading to abnormality of gas lock.
Please also refer to U.S. Patent Publication no. 2015/0291251 ('251 hereafter), it disclosed that “When in use, the handle of the break is pressed so the break line 13 drives the arm 12 to move toward the oil chamber 102 (see FIG. 4), namely driving the piston 20 to move horizontally through the arm 12, so the hydraulic oil stored in the oil chamber 102 can be squeezed out by the piston 20 to drive the break pad 11 in the receiving space 101. When the handle of the break is released, the resilient unit 30 can push the piston 20 back to its original position. Furthermore, the knob 40 is used to drive the piston 20 to axially move on the positioning portion 121 to conduct fine-tuning of the break.” Please note that the knob of '251 is rotated to move axially to drive the rod of '251 and the piston of '251. It should be known that the moving directions of the knob and the rod are the same and in parallel. That is, the moving directions of the knob and the rod are in the axial direction of the rod. It may make the torque be zero sometimes.
In view of this problem, the present invention aims to provide a solution to overcome such a drawback.